167 lines
7.3 KiB
Plaintext
167 lines
7.3 KiB
Plaintext
menu "Firmware loader"
|
|
|
|
config FW_LOADER
|
|
tristate "Firmware loading facility" if EXPERT
|
|
default y
|
|
help
|
|
This enables the firmware loading facility in the kernel. The kernel
|
|
will first look for built-in firmware, if it has any. Next, it will
|
|
look for the requested firmware in a series of filesystem paths:
|
|
|
|
o firmware_class path module parameter or kernel boot param
|
|
o /lib/firmware/updates/UTS_RELEASE
|
|
o /lib/firmware/updates
|
|
o /lib/firmware/UTS_RELEASE
|
|
o /lib/firmware
|
|
|
|
Enabling this feature only increases your kernel image by about
|
|
828 bytes, enable this option unless you are certain you don't
|
|
need firmware.
|
|
|
|
You typically want this built-in (=y) but you can also enable this
|
|
as a module, in which case the firmware_class module will be built.
|
|
You also want to be sure to enable this built-in if you are going to
|
|
enable built-in firmware (CONFIG_EXTRA_FIRMWARE).
|
|
|
|
if FW_LOADER
|
|
|
|
config EXTRA_FIRMWARE
|
|
string "Build named firmware blobs into the kernel binary"
|
|
help
|
|
Device drivers which require firmware can typically deal with
|
|
having the kernel load firmware from the various supported
|
|
/lib/firmware/ paths. This option enables you to build into the
|
|
kernel firmware files. Built-in firmware searches are preceded
|
|
over firmware lookups using your filesystem over the supported
|
|
/lib/firmware paths documented on CONFIG_FW_LOADER.
|
|
|
|
This may be useful for testing or if the firmware is required early on
|
|
in boot and cannot rely on the firmware being placed in an initrd or
|
|
initramfs.
|
|
|
|
This option is a string and takes the (space-separated) names of the
|
|
firmware files -- the same names that appear in MODULE_FIRMWARE()
|
|
and request_firmware() in the source. These files should exist under
|
|
the directory specified by the EXTRA_FIRMWARE_DIR option, which is
|
|
/lib/firmware by default.
|
|
|
|
For example, you might set CONFIG_EXTRA_FIRMWARE="usb8388.bin", copy
|
|
the usb8388.bin file into /lib/firmware, and build the kernel. Then
|
|
any request_firmware("usb8388.bin") will be satisfied internally
|
|
inside the kernel without ever looking at your filesystem at runtime.
|
|
|
|
WARNING: If you include additional firmware files into your binary
|
|
kernel image that are not available under the terms of the GPL,
|
|
then it may be a violation of the GPL to distribute the resulting
|
|
image since it combines both GPL and non-GPL work. You should
|
|
consult a lawyer of your own before distributing such an image.
|
|
|
|
config EXTRA_FIRMWARE_DIR
|
|
string "Firmware blobs root directory"
|
|
depends on EXTRA_FIRMWARE != ""
|
|
default "/lib/firmware"
|
|
help
|
|
This option controls the directory in which the kernel build system
|
|
looks for the firmware files listed in the EXTRA_FIRMWARE option.
|
|
|
|
config FW_LOADER_USER_HELPER
|
|
bool "Enable the firmware sysfs fallback mechanism"
|
|
help
|
|
This option enables a sysfs loading facility to enable firmware
|
|
loading to the kernel through userspace as a fallback mechanism
|
|
if and only if the kernel's direct filesystem lookup for the
|
|
firmware failed using the different /lib/firmware/ paths, or the
|
|
path specified in the firmware_class path module parameter, or the
|
|
firmware_class path kernel boot parameter if the firmware_class is
|
|
built-in. For details on how to work with the sysfs fallback mechanism
|
|
refer to Documentation/driver-api/firmware/fallback-mechanisms.rst.
|
|
|
|
The direct filesystem lookup for firmware is always used first now.
|
|
|
|
If the kernel's direct filesystem lookup for firmware fails to find
|
|
the requested firmware a sysfs fallback loading facility is made
|
|
available and userspace is informed about this through uevents.
|
|
The uevent can be suppressed if the driver explicitly requested it,
|
|
this is known as the driver using the custom fallback mechanism.
|
|
If the custom fallback mechanism is used userspace must always
|
|
acknowledge failure to find firmware as the timeout for the fallback
|
|
mechanism is disabled, and failed requests will linger forever.
|
|
|
|
This used to be the default firmware loading facility, and udev used
|
|
to listen for uvents to load firmware for the kernel. The firmware
|
|
loading facility functionality in udev has been removed, as such it
|
|
can no longer be relied upon as a fallback mechanism. Linux no longer
|
|
relies on or uses a fallback mechanism in userspace. If you need to
|
|
rely on one refer to the permissively licensed firmwared:
|
|
|
|
https://github.com/teg/firmwared
|
|
|
|
Since this was the default firmware loading facility at one point,
|
|
old userspace may exist which relies upon it, and as such this
|
|
mechanism can never be removed from the kernel.
|
|
|
|
You should only enable this functionality if you are certain you
|
|
require a fallback mechanism and have a userspace mechanism ready to
|
|
load firmware in case it is not found. One main reason for this may
|
|
be if you have drivers which require firmware built-in and for
|
|
whatever reason cannot place the required firmware in initramfs.
|
|
Another reason kernels may have this feature enabled is to support a
|
|
driver which explicitly relies on this fallback mechanism. Only two
|
|
drivers need this today:
|
|
|
|
o CONFIG_LEDS_LP55XX_COMMON
|
|
o CONFIG_DELL_RBU
|
|
|
|
Outside of supporting the above drivers, another reason for needing
|
|
this may be that your firmware resides outside of the paths the kernel
|
|
looks for and cannot possibly be specified using the firmware_class
|
|
path module parameter or kernel firmware_class path boot parameter
|
|
if firmware_class is built-in.
|
|
|
|
A modern use case may be to temporarily mount a custom partition
|
|
during provisioning which is only accessible to userspace, and then
|
|
to use it to look for and fetch the required firmware. Such type of
|
|
driver functionality may not even ever be desirable upstream by
|
|
vendors, and as such is only required to be supported as an interface
|
|
for provisioning. Since udev's firmware loading facility has been
|
|
removed you can use firmwared or a fork of it to customize how you
|
|
want to load firmware based on uevents issued.
|
|
|
|
Enabling this option will increase your kernel image size by about
|
|
13436 bytes.
|
|
|
|
If you are unsure about this, say N here, unless you are Linux
|
|
distribution and need to support the above two drivers, or you are
|
|
certain you need to support some really custom firmware loading
|
|
facility in userspace.
|
|
|
|
config FW_LOADER_USER_HELPER_FALLBACK
|
|
bool "Force the firmware sysfs fallback mechanism when possible"
|
|
depends on FW_LOADER_USER_HELPER
|
|
help
|
|
Enabling this option forces a sysfs userspace fallback mechanism
|
|
to be used for all firmware requests which explicitly do not disable a
|
|
a fallback mechanism. Firmware calls which do prohibit a fallback
|
|
mechanism is request_firmware_direct(). This option is kept for
|
|
backward compatibility purposes given this precise mechanism can also
|
|
be enabled by setting the proc sysctl value to true:
|
|
|
|
/proc/sys/kernel/firmware_config/force_sysfs_fallback
|
|
|
|
If you are unsure about this, say N here.
|
|
|
|
config FW_CACHE
|
|
bool "Enable firmware caching during suspend"
|
|
depends on PM_SLEEP
|
|
default y if PM_SLEEP
|
|
help
|
|
Because firmware caching generates uevent messages that are sent
|
|
over a netlink socket, it can prevent suspend on many platforms.
|
|
It is also not always useful, so on such platforms we have the
|
|
option.
|
|
|
|
If unsure, say Y.
|
|
|
|
endif # FW_LOADER
|
|
endmenu
|